Voluntary compliance with tax laws, the foundation of the U.S. tax system, could be undermined if the public perceives that federal workers and former federal workers successfully evade their tax obligations. Internal Revenue Service (IRS) records indicate that federal workers and annuitants, and IRS workers in particular, appear to be more compliant in meeting their tax responsibilities than the general population. Nonetheless, IRS records indicate that some federal workers and annuitants are not fulfilling their tax responsibilities and owe the federal government about $2.5 billion in outstanding taxes. In its attempt to improve management and collection of federal taxes owed by federal workers and annuitants, IRS faces the same issues hindering its ability to manage and collect unpaid taxes of the general population. With respect to IRS' efforts to improve compliance among federal workers and annuitants, IRS must first be able to determine how effective its program for this purpose has been and what, if any, modifications are needed to ensure that the program meets its objectives.